BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a mobile terminal with a data relay function, and
a communication control method thereof.
Related Background Art
[0002] In general wireless LAN communication, an access point at public facilities or at
home is connected through a broadband line to a network and a session is established
between a communication terminal with a wireless LAN function and the access point
to enable the communication terminal to implement communication with the network.
Examples of such communication terminals with the wireless LAN function include personal
computers, game machines, cell phones, and so on.
[0003] In a wireless LAN system, the communication terminal normally connects (or belongs)
to an optimal access point according to conditions of radio waves sent from access
points. A handover process is carried out with changeover to another optimal access
point due to movement of the communication terminal. Patent Document 1 below describes
a method of performing a reconnection process upon the handover in a short time even
during quick movement of the communication terminal. This method is to temporarily
set the number of retransmissions smaller than the preset number of retransmissions
of connection cancellation information in transmission of the connection cancellation
information from the communication terminal to a base station connected before the
handover and thereby reduce a time from detection of a base station to be connected
after the handover, to connection to the base station.
Patent Document 1: Japanese Patent Application Laid-open No.
2005-323034
SUMMARY OF THE INVENTION
[0004] If the function of the access point is loaded on such a mobile terminal as a cell
phone, the communication terminal can perform communication with the network through
the mobile terminal even at places where there is neither a home wireless LAN nor
a public wireless LAN. However, when a user uses the mobile terminal as an access
point, the mobile terminal is usually placed near the communication terminal, and
thus the communication terminal connected once to the mobile terminal continues to
belong to the mobile terminal. As a result, even if the communication terminal moves
into an area of a home wireless LAN or public wireless LAN, it will not be handed
over to a base station of the wireless LAN and the mobile terminal will continuously
transmit information (a beacon signal) necessary for communication.
[0005] The present invention has been accomplished in order to solve the above problem and
an object of the present invention is to provide a mobile terminal capable of urging
a communication terminal connecting (or belonging) thereto, to carry out a handover,
and a communication control method thereof.
[0006] A mobile terminal according to the present invention is a mobile terminal comprising:
relay means for relaying data transmitted between another communication terminal and
a network; and control means for controlling the relay means, based on a location
state in a radio communication network derived based on a reception situation of a
signal from a base station of the radio communication network different from a mobile
communication network, wherein the control means cancels a connection to the another
communication terminal when the mobile terminal is located inside an area of the radio
communication network.
[0007] A communication control method according to the present invention is a communication
control method in a mobile terminal with relay means for relaying data transmitted
between another communication terminal and a network, the communication control method
comprising: a control step of controlling the relay means, based on a location state
in a radio communication network derived based on a reception situation of a signal
from a base station of the radio communication network different from a mobile communication
network, wherein the control step is to cancel a connection to the another communication
terminal when the mobile terminal is located inside an area of the radio communication
network.
[0008] Since the mobile terminal and the communication control method as described above
are configured to cancel the connection to the another communication terminal connecting
to the mobile terminal, when the mobile terminal moves into the area of the radio
communication network, the communication terminal stops belonging to the mobile terminal.
The communication terminal is given a chance of the handover in this manner, whereby
the communication terminal connecting (or belonging) to the mobile terminal is urged
to carry out the handover.
[0009] The mobile terminal of the present invention is preferably configured as follows:
it further comprises monitoring means for monitoring a connection request signal transmitted
from the another communication terminal the connection to which was cancelled; the
control means deactivates the relay means if a destination of the connection request
signal monitored by the monitoring means is the base station of the radio communication
network, and establishes a connection to the another communication terminal in order
to relay data communication associated with the another communication terminal if
the destination is the mobile terminal.
[0010] In this case, the monitoring means monitors to which access point the another communication
terminal stopping belonging to the mobile terminal transmits the connection request
signal. If the communication terminal requests the connection to the base station
of the radio communication network, the relay means of the mobile terminal is deactivated;
if the communication terminal requests the connection to the mobile terminal, the
communication terminal is again connected to the mobile terminal. As the relay function
(access point function) is operated only if a connection is again requested by the
communication terminal the connection to which was cancelled, the power of the mobile
terminal consumed for the relay function can be reduced.
[0011] Since these mobile terminal and communication control method are configured to cancel
the connection to the another communication terminal connecting to the mobile terminal
when the mobile terminal moves into the area of the radio communication network, the
communication terminal connecting (or belonging) to the mobile terminal can be urged
to carry out the handover.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012]
Fig. 1 is a drawing showing a functional configuration of a cell phone according to
an embodiment.
Fig. 2 is a drawing showing a hardware configuration of the cell phone shown in Fig.
1.
Fig. 3 is a flowchart showing an operation of the cell phone shown in Fig. 1.
Fig. 4 is a sequence diagram showing a cooperative operation among a cell phone, a
digital camera, and a wireless LAN.
Fig. 5 is a sequence diagram showing a cooperative operation among a cell phone, a
digital camera, and a wireless LAN.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0013] Embodiments of the present invention will be described below in detail with reference
to the accompanying drawings. In the embodiments the mobile terminal according to
the present invention is applied to a cell phone. In the description of the drawings
identical or equivalent elements will be denoted by the same reference symbols, without
redundant description.
[0014] First, configurations and functions of a cell phone according to an embodiment will
be described using Figs. 1 and 2. Fig. 1 is a drawing showing a functional configuration
of the cell phone. Fig. 2 is a drawing showing a hardware configuration of the cell
phone.
[0015] As shown in Fig. 1, the cell phone 1 can communicate with a mobile communication
network 2 through transmission and reception of signals to and from a base station
2a forming the mobile communication network 2. Furthermore, the cell phone 1 can also
communicate with a wireless LAN 3 through transmission and reception of signals to
and from a base station 3a forming the wireless LAN 3. It is noted herein that the
wireless LAN 3 is a communication network different from the mobile communication
network 2. The mobile communication network 2 and the wireless LAN 3 are connected
each to a backbone network 4.
[0016] The cell phone is equipped with an access point function to relay data transmitted
between a digital camera (another communication terminal) 5 and the network. The digital
camera 5 is equipped with a wireless LAN function.
[0017] The cell phone 1 has the following functional components: first receiver 11, first
determiner 12, second receiver 13, second determiner 14, relay unit (relay means)
15, monitoring unit (monitoring means ) 16, and relay controller (control means) 17.
[0018] As shown in Fig. 2, the cell phone 1 is composed of a CPU 101 to execute an operating
system, an application program, and others, a main memory unit 102 composed of a ROM
and a RAM, an auxiliary memory unit 103 composed of a memory or the like, a communication
control unit 104 to perform data communication through the mobile communication network
2 or the wireless LAN 3, a display unit 105 composed of a liquid crystal monitor or
the like, and an operation unit 106 composed of input keys or the like. Each of the
functions shown in Fig. 1 is implemented by making predetermined software retrieved
onto the CPU 101 and main memory unit 102, operating the communication control unit
104 under control of the CPU 101, and reading and writing data from and into the main
memory unit 102 or the auxiliary memory unit 103.
[0019] Referring back to Fig. 1, the first receiver 11 is a part that receives broadcast
information (signal) from the base station 2a of the mobile communication network
2. The first receiver 11 outputs the received broadcast information to the first determiner
12.
[0020] The first determiner 12 is a part that determines a location state of the cell phone
1 in the mobile communication network 2, based on a reception situation of the signal
from the base station 2a of the mobile communication network 2. For example, the first
determiner 12 determines that the cell phone 1 is located inside the area of the mobile
communication network 2, if the first receiver 11 receives the broadcast information;
otherwise, it determines that the cell phone 1 is located outside the area of the
mobile communication network 2. The first determiner 12 outputs the determination
result as first location information to the relay controller 17. The first location
information is information indicative of whether the cell phone 1 is located in the
mobile communication network 2 and, as described above, it is derived based on the
reception situation of the broadcast information from the base station 2a of the mobile
communication network 2.
[0021] The second receiver 13 is a part that receives a beacon (signal) from the base station
3a of the wireless LAN 3. The second receiver 13 outputs the received beacon to the
second determiner 14.
[0022] The second determiner 14 is a part that determines a location state of the cell phone
1 in the wireless LAN 3, based on a reception situation of the signal from the base
station 3a of the wireless LAN 3. For example, the second determiner 14 determines
that the cell phone 1 is located inside the area of the wireless LAN 3, if the second
receiver 13 receives the beacon; otherwise, it determines that the cell phone 1 is
located outside the area of the wireless LAN 3. Then the second determiner 14 outputs
the determination result as second location information to the relay controller 17.
The second location information is information indicative of whether the cell phone
1 is located in the wireless LAN 3 and, as described above, it is derived based on
the reception situation of the beacon from the base station 3a of the wireless LAN
3.
[0023] The relay unit 15 is a part that relays data transmitted between the digital camera
(another communication terminal) 5 and the network. The relay unit 15 initiates or
terminates transmission of a beacon according to a control signal input from the relay
controller 17 described below. When a connection is established between the cell phone
1 and the digital camera 5 by transmission of the beacon, the relay unit 15 becomes
able to relay data transmitted between the digital camera 5 and the mobile communication
network 2 and data transmitted between the digital camera 5 and the backbone network
4. At this time, the cell phone 1 functions as an access point.
[0024] The relay unit 15 also functions to cancel the connection to the digital camera 5
and to deactivate the relay function in accordance with a control signal fed from
the relay controller 17. The relay unit 15 transmits a belonging cancellation message
such as disauthentication (de-authentication) or disassociation to the digital camera
5 to cancel the connection to the digital camera 5. However, the connection cancellation
(belonging cancellation) method is not limited only to this. For example, the relay
unit 15 may execute the connection cancellation by reducing the transmission power
or by forcibly changing (or resetting) a radio setting such as a service set identifier
(SSID).
[0025] The monitoring unit 16 is a part that monitors a connection request signal transmitted
from the digital camera 5 the connection to which was cancelled. This connection request
signal is specifically a probe request. The monitoring unit 16 receives the probe
request, checks the SSID included in the request, and determines to which the digital
camera 5 requests a connection. Since the probe request is a broadcast signal, the
monitoring unit 16 can also monitor the probe request which the digital camera 5 transmitted
to the wireless LAN 3. The monitoring unit 16 generates connection request information
indicative of a destination of the probe request (object requested to connect to the
digital camera 5) and outputs the connection request information to the relay controller
17.
[0026] The relay controller 17 is a part that controls the relay unit 15, based on a location
state in the wireless LAN 3 derived based on a reception situation of the signal from
the base station 3a of the wireless LAN 3. The relay controller 17 controls the relay
unit 15, based on the first location information and the second location information.
[0027] With input of the first location information indicative of the location inside the
area of the mobile communication network 2 and input of the second location information
indicative of the location outside the area of the wireless LAN 3, the relay controller
17 determines that the relay unit is to be activated. Then the relay controller 17
generates a control signal for controlling the relay unit 15 to transmit a beacon,
and outputs it to the relay unit 15. This makes the relay unit 15 start transmission
of the beacon or continue its transmission process. As a result, the access point
function of the cell phone 1 is activated and the digital camera 5 becomes connectable
to the network.
[0028] If the relay controller 17 receives input of the second location information indicative
of the location inside the area of the wireless LAN 3 while the cell phone 1 connects
to the digital camera 5 or while the digital camera 5 belongs to the cell phone 1,
it determines that the connection to the digital camera 5 is to be cancelled. Then
the relay controller 17 generates a control signal for cancelling the connection to
the digital camera 5, and outputs it to the relay unit 15. This makes the relay unit
15 cancel the connection to the digital camera 5.
[0029] Thereafter, when the connection request information is fed from the monitoring unit
16, the relay controller 17 controls the relay unit 15, based on the signal. Specifically,
when the input is the connection request information indicating that the digital camera
5 requests a connection to the base station 3a of the wireless LAN 3, the relay controller
17 determines that the access point function is to be deactivated. Then the relay
controller 17 generates a control signal for deactivating the relay unit 15, and outputs
it to the relay unit 15. On the other hand, when the input is the connection request
information indicating that the digital camera 5 requests a connection to the cell
phone 1, the relay controller 17 determines that the cell phone is to connect to the
digital camera 5. Then the relay controller 17 generates a control signal for controlling
the relay unit to transmit a beacon, and outputs it to the relay unit 15. In this
case, the access point function of the cell phone 1 is resumed and the relay unit
15 connects to the digital camera 5 in order to relay data communication associated
with the digital camera 5.
[0030] The below will describe the operation of the cell phone shown in Fig. 1 and a communication
control method according to the present embodiment, using Figs. 3 to 5. Fig. 3 is
a flowchart showing the operation of the cell phone. Figs. 4 and 5 are sequence diagrams
showing cooperative operations among the cell phone, the digital camera, and the wireless
LAN.
[0031] It is assumed that the cell phone 1 is connected to the digital camera 5 and that
the cell phone 1 is functioning as an access point of the digital camera 5 (step S1).
Thereafter, when the second determiner 14 determines that the cell phone 1 has moved
into the area of the wireless LAN 3 (step S2; YES), the relay controller 17 determines
that the connection to the digital camera 5 is to be cancelled, and the relay unit
15 executes the connection cancellation process, based on the determination (step
S3, control step).
[0032] Thereafter, the monitoring unit 16 monitors the probe request transmitted from the
digital camera (step S4) and judges the destination of the request. If the destination
is the base station 3a of the wireless LAN 3 (step S5; wireless LAN), the relay controller
17 determines that the access point function is to be deactivated, and the relay unit
15 is deactivated based on the determination (step S6). At this time, the digital
camera 5 connects to the wireless LAN 3 and becomes able to execute data communication
with the network through the wireless LAN 3 (step S7).
[0033] On the other hand, if the destination of the probe request is the cell phone 1 (step
S5; cell phone), the relay controller 17 determines that the cell phone is to again
connect to the digital camera 5, and the relay unit 15 resumes the access point function
(step S8). This makes the digital camera 5 belong to the cell phone 1 and allows the
digital camera 5 to execute data communication with the network through the cell phone
1.
[0034] When the digital camera 5 switches its access point from the cell phone 1 to the
wireless LAN 3, the processing as shown in Fig. 4 is carried out. Specifically, while
the cell phone 1 and the digital camera 5 connect to each other (step S11), these
devices move into the area of the wireless LAN 3 (step S12), and, based on the determination
of the relay controller 17, the relay unit 15 sends a belonging cancellation message
to the digital camera 5 (step S 13, control step). This results in cancelling the
connection between the cell phone 1 and the digital camera 5.
[0035] Thereafter, the monitoring unit 16 monitors the probe request from the digital camera
5 (step S14). This monitoring operation is continuously executed during a period of
time T until the destination of the probe request is figured out. Thereafter, the
digital camera 5 sends the probe request to the base station 3a of the wireless LAN
3 (step S 15). This causes the digital camera 5 to connect to the wireless LAN 3,
thereby completing the handover (step S16). On the other hand, the relay controller
17 deactivates the relay unit 15 in the cell phone 1 (step S17).
[0036] When the digital camera 5 again uses the cell phone 1 as an access point, the processing
as shown in Fig. 5 is carried out. First, the processes of steps S21 to S24 are the
same as those of steps S11 to S 14. The monitoring unit 16 continuously executes the
monitoring process during a period of time T' until the destination of the probe request
is figured out. Thereafter, the digital camera 5 transmits the probe request to the
cell phone 1, e.g., for the reason of failure in connection to the wireless LAN 3
(step S25). Then the digital camera 5 again connects to the cell phone 1 (step S26).
[0037] In the present embodiment, as described above, when the cell phone 1 moves into the
area of the wireless LAN 3, the connection to the digital camera 5 connecting to the
cell phone 1 is cancelled and thus the digital camera 5 stops belonging to the cell
phone 1. As the digital camera 5 is given a chance of a handover in this manner, the
digital camera 5 connecting (or belonging) to the cell phone 1 is urged to carry out
the handover.
[0038] According to the present embodiment, the cell phone 1 is configured to monitor the
probe request transmitted from the digital camera 5 which stopped belonging to the
cell phone 1. If the digital camera 5 requests a connection to the base station 3a
of the wireless LAN 3, the relay unit 15 of the cell phone 1 is deactivated; if the
digital camera 5 requests a connection to the cell phone 1, the cell phone again connects
to the digital camera 5. Since the relay function (access point function) is operated
only when the connection is again requested by the digital camera 5 the connection
of which was cancelled, the power of the cell phone 1 consumed for the relay function
can be reduced. Furthermore, convenience is improved because the handover process
of the digital camera 5 is automatically carried out.
[0039] The present invention was described above in detail based on the embodiment thereof.
However, the present invention is not limited only to the above embodiment. The present
invention can be modified in many ways as described below, without departing from
the scope and spirit of the invention.
[0040] The above embodiment showed the example wherein the cell phone 1 determined the location
situation in the wireless LAN 3, but it is also possible to adopt a configuration
wherein the digital camera 5 determines the location situation in the wireless LAN
3 and notifies the cell phone 1 of the determination result (equivalent to the second
location information in the above embodiment). This configuration eliminates the need
for the mobile terminal to determine the location situation in the radio communication
network and thus reduces the load on the mobile terminal.
[0041] The above embodiment showed the wireless LAN 3 as the radio communication network,
but there are no restrictions on the type of the radio communication network. For
example, the present invention is also applicable to systems using WiMAX (Worldwide
Interoperability for Microwave Access). Furthermore, there are no restrictions on
the type of the mobile communication network, either. For example, the present invention
is also applicable to systems using W-CDMA (Wideband Code Division Multiple Access),
CDMA-2000, or LTE (Long Term Evolution).
[0042] The above embodiment showed the example of the cell phone 1 and the digital camera
5 as the mobile terminal and the another communication terminal, but there are no
restrictions on the type of the mobile terminal, and the type of the communication
terminal configured to communicate through the mobile terminal. For example, a personal
digital assistant (PDA) can be the mobile terminal and a portable game machine or
portable music player can be the another communication terminal.